The present invention relates to a semiconductor light-emitting device, and particularly to an AlGaInP-based red visible light semiconductor light-emitting device and a method of manufacturing the same.
Most of semiconductor light-emitting devices, e.g., semiconductor lasers are formed as index-guide structure in order to enhance performance.
AlGaInP-based red visible light semiconductor lasers of index-guide type are generally of loss-guide type in which a current confinement layer for confining a current path is made of GaAs whose band gap is smaller than that of a GaInP active layer and whose refractive index is larger than that of the GaInP active layer.
This AlGaInP-based semiconductor laser will be described below together with its manufacturing method.
As shown in FIG. 1, there is carried out a first epitaxial deposition process in which an n-type GaAs buffer layer 2, an n-type AlGaInP first cladding layer 3, a non-doped GaInP active layer 4, an AlGaInP second conductivity-type, i.e., p-type second cladding layer 5 and a p-type GaInP intermediate layer 6 are epitaxially deposited on a first conductivity-type, e.g., n-type GaAs substrate 1, in that order, thereby forming a laminated semiconductor layer.
Thereafter, as shown in FIG. 2, grooves 7 are formed at both sides of a stripe-shaped ridge 8 by etching to the extent that the grooves 7 reach the second cladding layer 5 but do not reach the active layer 4, for example, through the intermediate layer 6.
As shown in FIG. 3, there is carried out a second epitaxial deposition in which a first conductivity-type, e.g., n-type GaAs current confinement layer 9 is epitaxially deposited on the second cladding layer 5 so as to bury the grooves 7. The second epitaxial deposition is carried by selective epitaxial deposition. Specifically, in this case, a mask layer 10 for selective epitaxial deposition made of an insulating film such as an SiN film is epitaxially deposited on the ridge 8 and then GaAs is selectively and epitaxially deposited.
Thereafter, as shown in FIG. 4, the mask layer 10 is removed and there is carried out a third epitaxial deposition in which a second conductivity-type, i.e., p-type GaAs capping layer 11 is epitaxially deposited on the whole surface.
Then, although not shown, a first electrode is formed on the capping layer 11 so as to form an ohmic contact and a second electrode is formed on the back of the substrate 1 so as to form an ohmic contact.
This semiconductor laser is of so-called loss-guide structure because the current confinement layer 9 can absorb light emitted from the active layer 4 although a current is confined by the ridge 8 serving as a current path sandwiched by the current confinement layers 9.
However, because the loss-guide type semiconductor laser cannot avoid a problem of large power consumption, a semiconductor laser should preferably be formed as a real-guide type one in order to reduce a power consumption. In order to realize the real-guide type semiconductor laser, it is proposed that the current confinement layer 9 is made of AlGaInP whose band gap is smaller than that of the active layer 4 and whose refractive index is larger than that of the active layer 4. However, this AlGaInP-based semiconductor cannot be epitaxially deposited on uneven surface satisfactorily on which the ridge 8 is formed as shown in FIG. 2, e.g., AlGaInP-based semiconductor cannot be epitaxially deposited on a {111} crystal plane, for example, satisfactorily. As a result, dislocation occurs considerably, resulting in a semiconductor layer with many distortions. Therefore, a semiconductor laser with satisfactory laser characteristics cannot be made.